Abstract: A method is provided for setting a timing of phase modulation by a target phase modulator within an optical transmitter which performs 2n order phase shift keying, n being a natural number equal to or more than two. The method is provided with: feeding a specific pattern to the optical transmitter to allow the xPSK transmitter to emit an optical carrier in accordance with the specific pattern; receiving the optical carrier by a delay interferometer; converting a pair of light signals emitted from constructive and destructive outputs of the delay interferometer into an electrical signal; detecting a peak to peak value of the electrical signal; and setting the timing of the phase modulation by the target phase modulator so as to minimize the peak to peak value of the electrical signal.

Abstract: In the optical communication device and the optical communication system using DPSK modulation whose cost is low, whose size is small and whose power consumption is low, the N:1 multiplexer 125 generates a serial signal by multiplexing a parallel signal coded by the DPSK modulation coding units 115˜117 bit by bit on a time division basis. The electric-phase modulation optical converter 127 converts a serial signal into a phase modulation light. The N-bit delay interferometer 132 executes DPSK decoding with respect to a phase modulation light by comparison with an N-bit preceding optical signal. The optical-electric signal converter 134 converts a decoded intensity modulation light into an electric signal. The N:1 demultiplexer 136 divides an electric signal converted by the optical-electric signal converter 134 into a number N of signals bit by bit on a time division basis.

Abstract: Transmission-side communication apparatus 100 using a DQPSK (differential quadrature phase-shift keying) scheme is provided with: optical carrier generation section 102 which generates an optical carrier the frequency of which switches among a plurality of different frequencies within one symbol period; and modulation section 103 with which DQPSK-modulates the optical carrier generated by the optical carrier generation means in accordance with a modulation signal at an interval of the symbol period. There are provided: single delay interference section 121 which receives an optical signal obtained by DQPSK-modulating an optical carrier the frequency of which switches among a plurality of different frequencies within one symbol period and outputs an output light obtained by causing the optical signal 104 and a delay optical signal thereof to interfere with each other; and photoelectric conversion section 124 which converts the output light outputted by the delay interference means to an electric signal.

Abstract: The present invention converts each of the optical differential signals from DPSK demodulator from an optical signal into an electrical signal by using optical-electrical signal converters. Thereafter, each electrical signal is subjected to amplification adjustment at an appropriate amplification factor by variable amplifier, and an appropriate delay amount is added to each electrical signal by variable delay line, and thereafter data discrimination is performed by discriminator. Since two differential signals after DPSK demodulation are subjected to amplitude and delay adjustments, the need for optical parts is obviated enabling the use of electric circuits which can be integrated. Thus, the cost of the optical reception device will be reduced. Moreover, the since electric signals whose phases and amplitudes are equalized are inputted to discriminator, erroneous determination of data at discriminator will be reduced.

Abstract: The present invention provides a light receiving apparatus using the DQPSK demodulation method. The light receiving apparatus comprises: one Mach-Zehnder interferometer for branching a received light signal into light signals at two arms to allow the branched two light signals to interfere with each other; one balanced photoelectric converter for converting the two interfered light signals, by using the Mach-Zehnder interferometer, into an electric signal corresponding to a difference between light intensities of the two light signals; and a phase adjuster for dynamically shifting the phase of a light signal passed through one of the two arms at the Mach-Zehnder interferometer.

Abstract: A method is provided for setting a timing of phase modulation by a target phase modulator within an optical transmitter which performs 2n order phase shift keying, n being a natural number equal to or more than two. The method is provided with: feeding a specific pattern to the optical transmitter to allow the xPSK transmitter to emit an optical carrier in accordance with the specific pattern; receiving the optical carrier by a delay interferometer; converting a pair of light signals emitted from constructive and destructive outputs of the delay interferometer into an electrical signal; detecting a peak to peak value of the electrical signal; and setting the timing of the phase modulation by the target phase modulator so as to minimize the peak to peak value of the electrical signal.

Abstract: Transmission-side communication apparatus 100 using a DQPSK (differential quadrature phase-shift keying) scheme is provided with: optical carrier generation section 102 which generates an optical carrier the frequency of which switches among a plurality of different frequencies within one symbol period; and modulation section 103 with which DQPSK-modulates the optical carrier generated by the optical carrier generation means in accordance with a modulation signal at an interval of the symbol period. There are provided: single delay interference section 121 which receives an optical signal obtained by DQPSK-modulating an optical carrier the frequency of which switches among a plurality of different frequencies within one symbol period and outputs an output light obtained by causing the optical signal 104 and a delay optical signal thereof to interfere with each other; and photoelectric conversion section 124 which converts the output light outputted by the delay interference means to an electric signal.

Abstract: The present invention converts each of the optical differential signals from DPSK demodulator from an optical signal into an electrical signal by using optical-electrical signal converters. Thereafter, each electrical signal is subjected to amplification adjustment at an appropriate amplification factor by variable amplifier, and an appropriate delay amount is added to each electrical signal by variable delay line, and thereafter data discrimination is performed by discriminator. Since two differential signals after DPSK demodulation are subjected to amplitude and delay adjustments, the need for optical parts is obviated enabling the use of electric circuits which can be integrated. Thus, the cost of the optical reception device will be reduced. Moreover, the since electric signals whose phases and amplitudes are equalized are inputted to discriminator, erroneous determination of data at discriminator will be reduced.

Abstract: In a communication system in which a plurality of communication terminals sequentially transfer data to a server during the respective transmission permissible periods assigned to the respective communication terminals, the communication terminal transfers a preamble for synchronization to the server at a time of starting the transmission permissible period, converts a data frame for every 8 bits into every 10 bit-code, and transmits to the server, the signal string with a code indicating the head added there, during the transmission permissible period, and turns a communication to the server into a zero signal state, during a period other than the transmission permissible period, while the server establishes a synchronization by reading the preamble for synchronization inserted into the signal string received from each of the communication terminals, converts a portion of the zero signal state of the signal string into a predetermined special code string, and inversely transforms the received signal string i

Abstract: In the optical communication device and the optical communication system using DPSK modulation whose cost is low, whose size is small and whose power consumption is low, the N:1 multiplexer 125 generates a serial signal by multiplexing a parallel signal coded by the DPSK modulation coding units 115˜117 bit by bit on a time division basis. The electric-phase modulation optical converter 127 converts a serial signal into a phase modulation light. The N-bit delay interferometer 132 executes DPSK decoding with respect to a phase modulation light by comparison with an N-bit preceding optical signal. The optical-electric signal converter 134 converts a decoded intensity modulation light into an electric signal. The N:1 demultiplexer 136 divides an electric signal converted by the optical-electric signal converter 134 into a number N of signals bit by bit on a time division basis.

Abstract: The present invention provides a light receiving apparatus using the DQPSK demodulation method. The light receiving apparatus comprises: one Mach-Zehnder interferometer for branching a received light signal into light signals at two arms to allow the branched two light signals to interfere with each other; one balanced photoelectric converter for converting the two interfered light signals, by using the Mach-Zehnder interferometer, into an electric signal corresponding to a difference between light intensities of the two light signals; and a phase adjuster for dynamically shifting the phase of a light signal passed through one of the two arms at the Mach-Zehnder interferometer.

Abstract: Transmission delay time measurement is performed on a signal propagation path between respective points of two printed circuit boards connected by a coaxial cable. Measurement is made of a frequency-domain response of the cable and a first time-domain response of the propagation path at its sending point and a second time-domain response of the propagation path at its receiving point. From the first time-domain response and the frequency-domain response, estimation is made of a third time-domain response of the propagation path that would be observed at the receiving point if there is no waveform distortion on the surface of the printed circuit boards. Time-domain correlation is calculated between the second and third time-domain responses. A first delay time is determined from the estimated time-domain response and a second delay time is determined from the correlation. The first and second delay times are summed to yield the transmission delay time of the propagation path.

Abstract: Transmission delay time measurement is performed on a signal propagation path between respective points of two printed circuit boards connected by a coaxial cable. Measurement is made of a frequency-domain response of the cable and a first time-domain response of the propagation path at its sending point and a second time-domain response of the propagation path at its receiving point. From the first time-domain response and the frequency-domain response, estimation is made of a third time-domain response of the propagation path that would be observed at the receiving point if there is no waveform distortion on the surface of the printed circuit boards. Time-domain correlation is calculated between the second and third time-domain responses. A first delay time is determined from the estimated time-domain response and a second delay time is determined from the correlation. The first and second delay times are summed to yield the transmission delay time of the propagation path.

Abstract: A clock identification and reproduction circuit which synchronizes a clock signal with an input signal includes a voltage controlled generator for generating a clock signal, a phase comparator for detecting a phase difference between an input signal and a clock signal to generate a phase difference signal according to the phase difference, and a filter for synchronizing a clock signal of the voltage controlled generator in response to a phase difference signal, in which the phase comparator generates a phase difference signal when a specific pulse waveform of a pulse of an input signal changes.

Abstract: In a communication system in which a plurality of communication terminals sequentially transfer data to a server during the respective transmission permissible periods assigned to the respective communication terminals, the communication terminal transfers a preamble for synchronization to the server at a time of starting the transmission permissible period, converts a data frame for every 8 bits into every 10 bit-code, and transmits to the server, the signal string with a code indicating the head added there, during the transmission permissible period, and turns a communication to the server into a zero signal state, during a period other than the transmission permissible period, while the server establishes a synchronization by reading the preamble for synchronization inserted into the signal string received from each of the communication terminals, converts a portion of the zero signal state of the signal string into a predetermined special code string, and inversely transforms the received signal string i

Abstract: In order to produce a photo-mask for a modified illumination, corrective patterns are added to and/or deleted from each target area of a design pattern so as to minimize a deformation of an optical image on a photo-resist layer, and the corective patterns are calcualted by using algebraic equations without a trial-and-error.